The present invention generally relates to an auger feeder, wherein powder within a cylinder is metered and discharged in accordance with the rotation angle of a screw rotated within the cylinder, so that a given amount of power is discharged to fill containers.
Conventionally, in this type of auger feeder, a cylindrical metering portion is provided on the lower end portion of a funnel (so-called hopper) for holding the powder, a rotary shaft is inserted downwards from above into the funnel, and an auger screw which is loosely engaged within the cylindrical metering portion is secured to the lower end of the rotary shaft. The given amount of powder is discharged into a container through a resistor provided at the lower-end opening in accordance with the rotating angle of the screw.
The above-described auger feeder is used to supply a comparatively large capacity of granules, such as 10 grams, 100 grams and so on, to fill the containers. Generally, a rotary mechanism for an auger screw, a funnel for accommodating the weighed material such as powder or the like are secured together as one component of the filler, so that they are adapted not to be dismantled or assembled easily. Generally strict consideration is not given to preventing the mixing in of foreign matter such as dust in the operation step of discharging the weighed powder.
When powder such as medicine or the like is filled into vials or the like by the use of the above-described auger feeder, various problems are caused. Namely, an extremely strict sanitation control is required in the case of medicine or the like. Members and mechanisms, such as the auger screw, auger shaft, funnel and so on, which come into contact with the weighed material, are required to be dismantled and sterilized from time to time, so that the dismantling operation is required to be easily effected and the assembling operation is required to be easily effected after the sterilizing operation. However, in the conventional auger feeder, the auger shaft, the funnel and so on are secured as described above, so that the dismantling operation and the assembling operation are not easily effected. Also, mixtures of foreign material such as dust are required to be completely excluded from the process of filling the powder into the funnel and the process of discharging the powder into vials. Consideration is required to be given to preventing foreign material, such as dust floating in the air or falling from the portion of the machine where moving parts are frictionally engaged from being mixed with the weighed powder. In the conventional auger feeder, however, consideration is not given to such exclusion. Also, in the case of medicines such as bulk pharmaceuticals, normally powder in a small amount such as, for example, 50 mg is required to be discharged into vials or the like. But conventionally it is difficult to discharge and fill such a small amount of powder with high accuracy, because the conventional auger feeder discharges a comparatively large amount of material as described above.
In addition, in the above-described auger feeder, a resistance member such as a mesh is provided at the outlet disposed at the lower end of the metering part in order to prevent the natural falling of powdery particles to be metered. The resistance member, for example, consists of a mesh of cross knit filaments in a radial configuration. There is a limitation to these resistance members if the metering accuracy is to be improved. Let it be assumed that a predetermined amount of powdery particles to be fed is as small as 10 mg, 100 mg or the like, which is less than 1 g. When the powder particles which have adhered to the lower side of the resistance member drop all together, the amount to be fed becomes different from the predetermined amount. Further, when a powder to be fed is a very expensive medicine and the metering accuracy is required to be less than 1% so as to assure the uniformity of content, the conventional resistance members are not capable of achieving the above-described metering accuracy.